Parts of the Frame

PARTS OF THE FRAME

A bicycle frame consists of several tubes, each with a specific name and function. Understanding the frame's anatomy helps in discussing bicycle fit, specifications, and components.

• Top tube: Runs horizontally (or slightly angled) from the head tube to the seat tube.
• Down tube: Runs diagonally from the head tube down to the bottom bracket shell. The largest and strongest tube on the frame.
• Seat tube: The vertical tube that holds the seatpost, running from the bottom bracket to the seat cluster.
• Head tube: The short tube at the front of the bicycle that holds the fork steerer tube via the headset bearings.
• Bottom bracket shell: The cylindrical housing at the bottom of the frame. It contains the bottom bracket bearings, which the crankset spindle passes through.
• Seat stay: Two thin tubes running from the top of the seat tube down to the rear dropouts.
• Chain stay: Two tubes running from the bottom bracket shell back to the rear dropouts.
• Rear dropout: The slot at the end of the seat stays and chain stays into which the rear axle fits.